With the advancement of metal organic chemical vapor deposition method and molecular beam epitaxy method using gallium nitride (GaN), red, green, and blue light-emitting diodes (LEDs) capable of realizing high-luminance white light have been developed.
LEDs do not contain environmentally hazardous substances, such as mercury (Hg), which are used in conventional lighting apparatuses, such as incandescent lamps or fluorescent lamps. Consequently, LEDs are environmentally friendly. In addition, LEDs exhibit long life spans and low power consumption. As a result, LEDs have replaced conventional light sources. A core competitive factor of LEDs is the realization of high luminance based on a high-efficiency, high-output chip and packaging technology.
In order to realize high luminance, it is important to increase optical extraction efficiency. In order to increase optical extraction efficiency, various methods have been studied using a flip-chip structure, surface texturing, a patterned sapphire substrate (PSS), photonic crystal technology, and an anti-reflection layer structure.
One conventional light-emitting device is disclosed in U.S. Pat. No. 7,646,031 (2010 Jan. 12, title of the invention: LIGHT EMITTING DEVICE HAVING LIGHT EMITTING ELEMENTS). In the disclosed light-emitting device, LEDs 1 are arranged in a zigzag fashion, rather than in a line, between electrode pads 32. As a result, freedom of design may be limited, and current may be locally crowded in the center of the light-emitting device. Furthermore, adjacent LEDs 1 are connected to each other via a single air bridge line 28. If the line 28 is disconnected, the entire light-emitting device becomes inoperable, with the result that the reliability of the light-emitting device is reduced.